By The Light Of The Moon: Deer Rutting

As I sat in my stand on the field’s edge, I glanced to the east just as the moon was clearing the treetops. Like thousands before me, I contemplated what, if any influence it had on deer movement. Would tonight be a good night to hunt? The moon was nearly full, and conventional wisdom said most activity took place after dark. Furthermore, the moon was just rising. It wouldn’t be overhead for several hours, and the latest moon theory said that peak activity occurs when the moon is directly overhead. Besides, it was only the first day of November. The rut was still at least a week away.

Bucks begin rubbing as soon as their velvet sheds. Rubbing intensifies leading up to the seeking phase, making this a good time to take rub lines into consideration when choosing a stand site.

Theories about the moon’s relationship to deer abound, and probably have for nearly as long as man has walked the earth. To quote writer Jeff Murray in his book Moon Struck, some hunters swear by the moon, others swear at it. Even today, researchers and non-professionals disagree on how the moon influences deer behavior. However, a pair of dedicated whitetail enthusiasts have joined forces to come up with some enlightening theories and a substantial body of evidence to support their contentions. Applying what they’ve learned could help you maximize your time afield this fall.

The name Charles J. Alsheimer is a familiar one to most serious whitetail hunters. If you’ve never heard it, just look closely at the photo credits in most major deer hunting magazines. Alsheimer has been hunting, observing and photographing whitetails for almost four decades. A name perhaps less familiar is Wayne Laroche. Laroche is an avid whitetail enthusiast too, and a professional wildlife biologist who has been hunting and studying whitetails for just as long.

Laying The Foundation
In 1994, the pair teamed up. Laroche’s interest in moon-phase theory began in the early 1990s. Traveling from his native Vermont to Maine, he noticed striking differences in rut sign and behavior from year to year, and he wanted to know why. Knowing from his research that moonlight affects fish, he wondered if it could have a similar effect on whitetails. Alsheimer’s interest began in the late 1980s, spawned from many hours afield photographing, observing and hunting deer. What he was seeing just didn’t jibe with the accepted theories at that time.

Laroche began compiling evidence. We know that a whitetail’s pineal gland responds to changes in the amount of daylight by releasing hormones, which ultimately triggers the reproductive cycle. The accepted doctrine was that daylight meant sunlight, and since this varies little from year to year, it seems plausible that the rut should be relatively consistent on an annual basis. However, the moon also produces light. Furthermore, the period of greatest moonlight varies from year to year, depending on when the full moon falls in the calendar year. Laroche noted that the brightest full moons occur in November and December.

He also uncovered another interesting fact. Most does are bred under a dark-moon period. Jumping ahead to an average 199-day gestation period, he calculated that most fawns are born within a day of the third-quarter moon. The adaptive advantage of this is obvious. Fawns born during a dark moon phase have a better chance of avoiding or escaping predators.

Based on this and other evidence, Laroche eventually formed a hypothesis. He believes decreasing amounts of daylight prime a doe’s reproductive cycle. Then more subtle changes occur with the amount of available light, cued by moonlight that triggers hormonal production by the pineal gland. Alsheimer explains in his book Hunting Whitetails by the Moon, “A northern doe’s estrogen level peaks around November 1 as does a buck’s sperm count. With both sexes poised to breed, it stands to reason a mechanism must be in place if the doe is to enter estrus and be bred under the darker phases of the moon, which is the third quarter to first quarter. That mechanism in the north is the second full moon after the autumnal equinox, which I call the rutting moon.”

Observing The Rut
Numerous research projects and myriad hours of anecdotal evidence have yet to produce any conclusive findings on how general deer activity corresponds to moon phase. However, many well-known whitetail authorities maintain there is a connection. Texan, John Wootters, a mainstay of Petersen’s Hunting, is one such authority. In his book Hunting Trophy Deer, Wootters had this to say: “I’ve seen scientific correlations that tended to show the phase of the moon has nothing to do with whitetail activity, if all other things are the same. Which convinces me that either the deer haven’t seen the same charts or all other things are never the same. I will go to my grave unshakably convinced that exactly the opposite is true, and that moon phase is critical to a hunter’s plans.”

Moderate sparring during the early part of the fall season will give way to all-out battles as the rut peaks. If you choose to rattle, vary the intensity to correspond with the animals' current levels of aggressiveness.

While the moon phase may have little affect on the day-to-day activity levels, Alsheimer and Laroche’s work has generated some enlightening evidence on how moon phase affects the rut, in terms of both timing and intensity. The widely accepted belief among most biologists is that peak breeding north of the Mason-Dixon line occurs around November 15 every year, and is set by photoperiod. Most of the evidence for this comes from measuring fetuses in the spring, and backdating. However, even biologists will admit this method has a 20-day margin of error. That means the actual peak breeding period could occur anytime within ten days before or after November 15. It is Alsheimer’s contention that this date varies annually according to how the moon phase corresponds to the calendar. He also believes that when the Rutting Moon falls during the first eight days of November, the rut’s intensity is greater.

When you consider that the rut is triggered by photoperiods, this only makes sense. The moon too is a source of light, which increases in intensity approaching the full moon. If you don’t believe the whitetail’s estrous cycle is correlated with the moon consider this: the lunar cycle is 29.5 days, and the whitetail estrous cycle is 28-29 days.

Knowing they faced an army of critics, Laroche and Alsheimer began intensively studying a group of deer under controlled conditions. Most notable in their findings thus far is that nearly 80 percent of mature does are breeding during a 14-day window predicted by Laroche’s hypothesis. Assuming Laroche’s theory is correct, it has direct application for the hunter.

Application
Pre-rut is generally considered a slow period. You’ll recall this is the first full moon after the fall equinox. It begins a couple days before the pre-rut moon and ends seven days before the rutting moon. It is still early fall. Though deer are growing their warm winter coats, temperatures are warm and deer, especially bucks, are less active. They tend to stick to their core areas and move mostly during the cooler hours of twilight and night. The cooling nights, however, signal deer that fall and winter are on the way. Feeding intensity picks up and deer begin switching from high-protein summer foods to fall foods that are rich in carbohydrates.

This is the time to hunt food sources, especially those close to bedding cover. You don’t want to hunt too close to bedding however, as you may move deer out of the area completely. You also want to stay away from rut hotspots. According to another whitetail authority, Mark Drury, this is one of the biggest mistakes hunters make. “Every year I see it. Guys do their scouting, and then come October first, they’re in there hunting their best rut spots. They burn their stands out because of over-anxiousness. By the time the rut arrives, every one is used up. Early in the season you can do some afternoon hunting in or near food sources, but save your good stands for the rut.”

The best situation is where you find food, water and cover in close proximity. One of the best food sources is acorns. Research has shown that where they occur, acorns are far and away the preferred food of whitetails. However, the predominant species over much of the whitetail’s range are red oaks. The red oak is a two-year species, producing a good crop only every other year, when conditions are favorable. White oaks, on the other hand, produce acorns every year. Thus they provide a more reliable food source from year to year.

One advantage of the pre-rut period is that bucks are still traveling in bachelor groups. While conventional wisdom says the rut is the best time to rattle, and that may well be true, I’ve found the pre-rut almost as good. Bucks are still in bachelor groups, but this is when they sort out the dominance hierarchy, the pecking order. This sorting is done mostly by sparring. Thus, the sound of clashing antlers is a familiar one. Furthermore, because many bucks are still vying for position, rattling is more likely to attract subordinate bucks. During the rut, most of the fighting is between dominant rivals of nearly equal stature, and may actually scare off subordinate bucks. There may be a minor flare up of rutting activity as roughly 10 percent of the does come into estrus around the pre-rut moon, but that will subside rapidly.

The Rutting Moon
As you get closer to the rutting moon (the second full moon after fall equinox), it’s time to shift your attention to rut stands. This is the time to start keying in on scrapes and rub lines. Like a loaded gun, bucks are now primed and ready to breed. They begin scraping intensively to advertise their readiness to females, and scrapes become the computer dating service of the whitetail woods. The beginning of this period is a good time to exploit a dominant buck’s jealous nature by introducing a bogus rival. Until the does come into estrus, about the only thing that will draw a mature buck out of hiding is competition. Start applying buck lure to scrape and rub lines.

Post-Rut
By the time the post-rut period arrives, 80-90 percent of the does have likely been bred. Hunters have pressured deer for several months, and bucks are worn down from the rut’s intensity. Because of this, Alsheimer believes “post-rut bucks can be the hardest of all whitetails to hunt.” He recommends hunting food sources close to the thickest cover you can find. One major advantage northern hunters have is the amount of snow on the ground now. Tracking can reveal a lot about movement patterns. A predominance of tracks leading from bedding to feeding likely indicate an afternoon trail, while those leading to bedding often indicate the opposite. Hunters should time their hunts accordingly.

Roughly 28 days after the peak of the first rut, a smaller, second rut occurs. This is when most of the remaining does are bred, mostly yearling does. This rut is less intense. However, by continuing to concentrate on the same cover, and the doe groups that inhabit it, you’ll automatically be putting yourself in the right place. While not as effective as during the first rut, rattling and calling also work now. I’ve had several friends and acquaintances say they’ve had moderate success rattling in does at this time of year, and often the bucks aren’t far behind.

Below the Mason-Dixon Line
While this moon-phase theory can be applied to the South as well, there are numerous mitigating factors, including climate, genetics, nutrition, sex ratio and radically different day lengths. Alsheimer cautions: “In some parts of the South, nothing makes sense when predicting the rut.” One of the biggest confounding factors involves adaptive strategies. Because of the persistent moderate climate, survival rate of fawns varies less in relation to when they were born. Thus, does aren’t locked into a fixed breeding window.

Another mitigating factor is genetics. Many parts of the South have been re-stocked with Northern deer, whose genetic hard wiring is tuned into Northern day length conditions. Mixing them with Southern genetic lines could result in intermediate breeding dates, and some evidence from Mississippi has demonstrated this. Many Southern states also have dense herds, which often results in poorer nutrition and skewed sex ratios, both of which can throw off the rut’s timing. Based on his observations and those of several other researchers, however, Alsheimer believes that in well-balanced herds with good nutrition, timing of the rut will be more consistent with his moon-phase theory.

It’s important to remember that some of those same factors that confound timing of the rut in the South may also apply to Northern deer, particularly concerning the population size and sex ratio. Numerous other factors such as weather conditions, temperature and hunting pressure can also wreak havoc on your hunting plans if your goal is to hit the peak of rut. Remember too that these are generalities, and for every rule there is an exception. Still, by using the moon-phase theory as a guideline, and hunting accordingly, you can increase your chances of scoring big this fall.